Aqueous printing pastes, for use in printing and dyeing thermoplastic fiber material, such as polyester textiles, have of necessity contained thickening agents in order to be sufficiently thick and non-flowing for proper application to the textile material. When heat is used, as is common with thermoplastic textiles, to fix the dyestuff on and in the fibers, many thickening agents of the art discolor and give a finished product having yellowed or muddy color values. Furthermore, thickening agents as used in the art, tend to retain dyestuff which was intended for the fibers. This retention of dyestuff by the thickening agent leads to reduced color yield on the fibers and to poor fastness properties, particularly poor crock fastness, poor bleed fastness, and poor wash fastness on first wash. Finally, thickening agents as used in the art lend a great deal of stiffness to the final product (which is not salable without an afterwash) and generally contribute to poor handle. In summary, thickening agents, as used in the art, are of such a chemical nature and used in such amounts that soaping or afterwash is necessitated or else the finished product will be discolored, have poor fastness properties and poor handle.
Soaping operations are expensive and to be avoided if possible. Not only do soaping operations involve an expenditure of time and materials, but such operations lead to increased plant effluent, which must be treated for ecological reasons. Furthermore, soaping operations involve a large energy expenditure to heat the wash water and dry the washed goods.
The art has addressed the above problems, which are inherent in printing thermoplastic textiles where heat fixation of the dye is practiced, by a number of approaches and improvements to the standard process. The standard process is taught in U.S. Pat. No. 2,663,612, which issued on Dec. 22, 1953 on application of J. W. Gibson, Jr.
One approach to avoiding the above-discussed disadvantages without after-wash is to reduce the amount of high-molecular weight thickener used and still achieve the requisite thickness by inclusion of an emulsified oil in the paste or liquor. That is to say that when the paste or liquor vehicle is a water and oil emulsion instead of water alone, the emulsion itself contributes sufficient thickness that very little high-molecular weight thickening agent is needed, and its removal from the finished product by soaping may be avoided, provided that the high-molecular weight thickening agent is sufficiently heat stable to not give appreciable discoloration during the thermal fixing step. Such an approach is taught in South African Patent No. 70/1414 which issued to H. P. Weber et al. of Mar. 3, 1970. This approach necessitates the removal of the volatile oil thickener and recovering the oil or dealing with the volatized oil as part of the air or water effluent.
A second approach to overcoming the above-discussed problems without after-wash of the final product involves dry thermal transfer printing, also known as sublimation printing. Sublimation or dry thermal transfer printing, taught in French Patent No. 1,223,330 and Swiss Patent No. 476,893, commonly involves the application of a thickened paste, containing sublimable dyestuff, to an auxiliary carrier. The printed auxiliary carrier is then applied to the thermoplastic textile and together with the textile is subjected to heat sufficient to cause the dyestuff to sublime from the carrier to the textile. Any high-molecular weight thickening agent present on the auxiliary carrier remains on the carrier, and the result is a remarkably sharp and clear textile print which requires no after soaping.
An object of this invention is to provide a printing process for use on thermoplastic textile material, involving the direct application of a printing paste to a thermoplastic textile and heat-fixation of the dyestuff on the textile material, to give remarkably sharp and clear prints of good fastness, without discoloration or impaired handle. A further object of this invention is to provide such a printing process without the use of a large amount of water such as is commonly used in soaping operations. Another object of this invention is to provide such a printing process without the use of volatile oils. The avoidance of pollution problems and anti-pollution expenses such as are encountered with large volumes of dyestuff-containing wash waters and with volatile oils, is a further object of this invention.
The objects of this invention have been met by a process for printing synthetic thermoplastic fibers without washing, comprising the steps of applying to the fibers an aqueous dispersion of a non-ionic organic colorant and a high-molecular weight thickener, subsequently drying the fibers, and finally heating the fibers to fix the colorant, wherein the thickener is used in an amount as low as 0.05% but less than 0.5%, preferably 0.05% to 0.2% and most preferably 0.1% to 0.2%, by weight of the aqueous dispersion and wherein the thickener is a compound of the formula: ##STR2## wherein R is hydrogen or lower alkyl,
R.sup.1 and R.sup.2 are hydrogen, sodium, potassium, ammonium, mono-lower alkyl ammonium, di-lower alkyl ammonium, tri-lower alkyl ammonium, or tetra-lower alkyl ammonium, PA1 m is 0 or 1, PA1 n is 2 - m, and PA1 y is 5000 to 50,000.
It has been discovered that the thickening agent of formula I are stable to heat, as commonly encountered in the thermal fixation step, and can be used to give thick pastes, even in extremely small amounts. The amount of high-molecular weight thickening agent used in the instant process is of the order of 1/5 to 1/25 of the amount of known-art thickening agents commonly used.
For the thickening agents of this invention to achieve full effectiveness in thickening power, it is advisable that the dyestuff be non-ionic and have no added salt or other electrolyte present. The dyestuff should also be finely divided, that is of colloidal dimensions, generally of a particle size in the range of about 0.5-50 microns in diameter. Dyestuffs for use in this invention can be obtained by milling, particularly wet milling, techniques well-known to the art. Disperse dyestuffs, free of added electrolyte, of the proper particle size are available commercially under the tradename Teraprint, as sold by CIBA-GEIGY Corporation, Ardsley, New York 10502.
As indicated above, full thickening power of the thickening agents used herein is realized in the absence of electrolytes. However, very small amounts of a dispersing agent or other surfactant are needed in the printing pastes of this invention in order to insure the proper wetting of the synthetic thermoplastic substrate fibers, since these fibers are hydrophobic and the printing pastes are water-based. Proper wetting of the hydrophobic fibers by the instant printing pastes is realized by inclusion in the printing paste formulation of less than 1% by weight of a non-ionic or an anionic surfactant. It is preferred to use no more than about 0.5% by weight of dispersing agent, the lower limit being determined as the least amount that will give a printing paste with satisfactory wetting power for the hydrophobic textile fibers. Exemplary or useful wetting agents for the practice of this invention are the non-ionic and anionic dispersing agents set out as emulsifiers in columns 8 and 9 of U.S. Pat. No. 3,728,087.
Examplary of the dyestuffs useful herein are the following:
______________________________________ CI Disperse CI CI Solvent CI Yellows Nos. Yellows Nos. 1 10345 18 12740 3 11885 30 21240 9 10375 13 58900 16 12700 42 10338 61 48005 CI Disperse CI CI Solvent CI Oranges Nos. Oranges Nos. 1 11080 7 12140 3 11005 7 11240 15 10350 CI Disperse CI CI Solvent CI Red Nos. Red Nos. 1 11110 23 26100 4 60755 24 26105 9 60505 25 26110 11 62015 13 11115 15 60710 CI Disperse CI CI Pigment CI Blue Nos. Red Nos. 3 61505 87 73310 5 62035 9 61115 14 61500 CI Vat CI 24 61515 Blue Nos. 26 63305 27 60767 1 73000 CI Disperse CI Violet Nos. CI Vat CI Red Nos. 1 61100 41 73300 4 61105 6 61140 CI Solvent CI 8 62030 Violet Nos. 12 11120 13 60725 ______________________________________
Also useful herein are the following disperse dyestuffs which do not have 5-digit CI numbers: